Today Intel is announcing its first SSD based on its own custom 6Gbps SATA controller. This new controller completely abandons the architecture of the old X25-M/320/710 SSDs and adopts an all new design with one major goal: delivering consistent IO latency.

All SSDs tend to fluctuate in performance as they alternate between writing to clean blocks and triggering defrag/garbage collection routines with each write. Under sequential workloads the penalty isn't all that significant, however under heavy random IO it can be a real problem. The occasional high latency blip can be annoying on a client machine (OS X doesn't respond particularly well to random high IO latency), but it's typically nothing more than a rare hiccup. Users who operate their drives closer to full capacity will find these hiccups to be more frequent. In a many-drive RAID array however, blips of high latency from each drive can destructively work together to reduce the overall performance of the array. In very large RAID arrays (think dozens of drives) this can be an even bigger problem.

In the past, we've recommended simply increasing the amount of spare area on your drive to combat these issues - a sort of bandaid that would allow the SSD controller to better do its job. With its latest controller, Intel tried to solve the root cause of the problem.

The launch vehicle for Intel's first 6Gbps SATA controller is unsurprisingly a high-end enterprise drive. Since the 2008 introduction of the X25-M, Intel has shifted towards prioritizing the enterprise market. All divisions of Intel have to be profitable and with high margins. The NAND Solutions Group (NSG) is no exception to the rule. With consumer SSDs in a race to the bottom in terms of pricing, Intel's NSG was forced to focus on an area that wouldn't cause mother Intel to pull the plug on its little experiment. The enterprise SSD market is willing to pay a premium for quality, and thus it became Intel's primary focus.

The first drive to use the new controller also carries a new naming system: the Intel SSD DC S3700. The DC stands for data center, which bluntly states the target market for this drive. While it's quite likely that we'll see a version appear in a high-end drive that could be used in a desktop, I don't know that we'll see a mobile version anytime soon for reasons I'll get to later.

The Drive

The S3700 comes in four capacities (100, 200, 400 and 800GB) and two form factors (2.5" and 1.8"). The 1.8" version is only available at 200GB and 400GB capacities. Intel sees market potential for a 1.8" enterprise SSD thanks to the increasing popularity of blade and micro servers. The new controller supports 8 NAND channels, down from 10 in the previous design as Intel had difficulty hitting customer requested capacity points at the highest performance while populating all 10 channels.

The S3700 is a replacement to the Intel SSD 710, and thus uses Intel's 25nm MLC-HET (High Endurance Technology) NAND. The S3700 is rated for full 10 drive writes per day (4KB random writes) for 5 years.

Intel SSD DC S3700 Endurance (4KB Random Writes, 100% LBA)

100GB

200GB

400GB

800GB

Rated Endurance

10DW x 5 years

10DW x 5 years

10DW x 5 years

10DW x 5 years

Endurance in PB

1.825 PB

3.65 PB

7.3 PB

14.6 PB

That's the worst case endurance on the drive, if your workload isn't purely random you can expect even more writes out of the S3700. Compared to the SSD 710, the S3700 sees an increase in endurance even without allocating as much NAND as spare area (~32% vs. 60% on the 710). The increase in endurance even while decreasing spare area comes courtesy of the more mature 25nm MLC-HET process. It's process maturity that's also responsible for Intel not using 20nm NAND on the S3700. We'll eventually see 20nm MLC-HET NAND, but just not now.

Pricing is also much more reasonable than the Intel SSD 710. While the 710 debuted at around $6.30/GB, the Intel SSD DC S3700 is priced at $2.35/GB. It's still more expensive than a consumer drive, but the S3700 launches at the most affordable cost per GB of any Intel enterprise SSD. A non-HET version would likely be well into affordable territory for high-end desktop users.

Intel SSD DC S3700 Pricing (MSRP)

100GB

200GB

400GB

800GB

Price

$235

$470

$940

$1880

The third generation Intel controller supports 6Gbps SATA and full AES-256 encryption. The controller is paired with up to 1GB of ECC DRAM (more on this later). Intel does error correction on all memories (NAND, SRAM and DRAM) in the S3700.

Like previous enterprise drives, the S3700 features on-board capacitors to commit any data in flight on the drive to NAND in the event of a power failure. The S3700 supports operation on either 12V, 5V or both power rails - a first for Intel. Power consumption is rated at up to 6W under active load (peak power consumption can hit 8.2W), which is quite high and will keep the S3700 from being a good fit for a notebook.

Performance & IO Consistency

Performance is much greater than any previous generation Intel enterprise SATA SSD:

Enterprise SSD Comparison

Intel SSD DC S3700

Intel SSD 710

Intel X25-E

Intel SSD 320

Capacities

100 / 200 / 400 / 800GB

100 / 200 / 300GB

32 / 64GB

80 / 120 / 160 / 300 / 600GB

NAND

25nm HET MLC

25nm HET MLC

50nm SLC

25nm MLC

Max Sequential Performance (Reads/Writes)

500 / 460 MBps

270 / 210 MBps

250 / 170 MBps

270 / 220 MBps

Max Random Performance (Reads/Writes)

76K / 36K

38.5K / 2.7K IOPS

35K / 3.3K IOPS

39.5K / 600 IOPS

Endurance (Max Data Written)

1.83 - 14.6PB

500TB - 1.5PB

1 - 2PB

5 - 60TB

Encryption

AES-256

AES-128

-

AES-128

Power Safe Write Cache

Y

Y

N

Y

Intel is also promising performance consistency with its S3700. At steady state Intel claims the S3700 won't vary its IOPS by more than 10 - 15% for the life of the drive. Most capacities won't see more than a 10% variance in IO latency (or performance) at steady state. Intel has never offered this sort of a guarantee before because its drives would vary quite a bit in terms of IO latency. The chart below shows individual IO latency at steady state (displayed in IOPS to make the graph a bit easier to read) for Intel's SSD 710:

Note the insane distribution of IOs. This isn't just an Intel SSD issue, click the buttons above to look at how Samsung's SSD 840 Pro and the SandForce based 330 do. All of these drives show anywhere from a 2x - 10x gap between worst and best case random write performance over time. Lighter workloads won't look as bad, and having more spare area will help keep performance high, but Intel claims the S3700 is able to tighten its IO latency down to a narrow band of about 10 - 15% variance.

Intel also claims to be able to service 99.9% of all 4KB random IOs (QD1) in less than 500µs:

To understand how the S3700 achieves this controlled IO latency, we need to know a bit more about Intel's older controllers. In researching for this article, I managed to learn more about Intel's first SSD controller than I ever knew before.

Post Your Comment

43 Comments

I'd say Samsung is about on par with Intel if you look at the number of major bugs requiring immediate firmware updates etc. Intel's rep took a bit of a hit when even they couldn't release an entirely bug free Sandforce drive IMO (though it wasn't a surprise).Reply

Not to mention the 8MB bug with their own controller. No product is safe, but Samsung, Intel, Crucial and Plextor seem the safest, with Samsung and Crucial being also very price competitive. But that's just how I see it. :D I have had 2 OCZ drives and not a single problem with either.Reply

"But with pricing like the S3700 is featuring, the days of Intel being competitive in the consumer space may be over..."THIS DRIVE IS NOT FOR THE CONSUMER SPACE!

"I'd rather see Intel take a two-tiered approach. By all means, keep putting out the enterprise drives for the high margins, but also keep a toe in the consumer market."THIS IS EXACTLY WHAT INTEL HAS RIGHT NOW! And no indication that will change. This doesn't just apply to the SSD space, they've had separate consumer and server CPU lines for decades.Reply

Spending big on a drive with strong endurance, hoping it will last 10 years, doesn't sound like a good idea to me. Reasons:

- other parts of the SSD may fail rather than NAND wear out- performance and price are still developing so rapidly that you probably won't want to use this drive in 5 years anymore anyway- see it lke this: if instead of paying 700$ now you'd go for a smaller drive with less endurance at 350$ you can use that 350$ (+interest) to buy a new drive in 5 years (if your SSD is really worn out by then). This one should be way faster and much bigger than the original drive, providing you much better value for the next 5 years. Plus if the old drive still works you could still use it in a less "enthusiastic" configuration.Reply

As far as I know, everyone in the consumer space but Intel chaches user data in the DRAM and they aren't dodging that either. For normal consumer use, I don't see why that would be any issue either. If you are worried about that last bit of data integrity, get an enterprise solution or a UPS, which should solve the issue, too. :)Reply

The new controller sounds very promising for all of us who have been waiting for a new Intel controller. I would expect Intel's consumer drives to eventually get the same controller and as far as the price concern, I bet most of the price premium is really from HET-MLC NAND vs regular MLC NAND. Regular consumers don't need 10 drive write per day and the drives should be much cheaper with just regular MLC NAND.Reply

Not caching user data writes in DRAM so that you can't lose them when the power goes out is all well and good, but what happens with indirection table updates which will have to happen AT THE SAME TIME and are inextricably linked? Losing an indirection table mapping to new user data that was just written is no less bad than losing the actual user data, because either way you're losing the data.

Intel has two options here... They can either write indirection table updates directly to NAND at the same time as the user data, or they can cache the indirection table updates only in DRAM and then write them to flash later. Obviously the former is the safest option and I presume this is what Intel is doing, but I've never seen anybody mention how they handle protecting the mapping table updates on any SSD, since they can arguably be MORE important than a little bit of user data due to the risk of losing absolutely everything on the drive if the table gets completely out of whack.Reply